The chief executive of AT&T has some advice for jobseekers: Brush up on your technical skills.

Randall Stephenson, who doubles as chairman of the Business Roundtable, says companies across the country have trouble finding suitable applicants for open positions. At AT&T, for example, the company interviews 11 people for every open job.

“The main issue that businesses face today is a skillset mismatch,” he said Tuesday in a conference call with reporters. “Our company is experiencing this today.”

Businesses have complained frequently for several years about the lack of skills they find in applicants, particularly for jobs that require strong math or science ability. That helps explain why the number of jobs being filled each month is lagging well behind an increase in job openings, which rose in June to the highest level since 2001.

“This is something we as a country have to deal with,” Stephenson said.

The shortage of skills, he said, is a chief reason why U.S. wages are growing so slowly. He said talented technicians are able to demand higher pay, but he also implied there’s less pressure to pay more to other workers with fewer skills.

“That’s a product of supply and demand,” he said.

Top executives surveyed by the Business Roundtable said they plan to spend and hire less in the third quarter compared to the spring and early summer, according to the group’s quarterly economic outlook survey. Stephenson said CEOs are worried about heightened global instability and the lack of initiatives in Washington that could give businesses a boost.

Stephenson said the best way to spur the economy – and by extension to help workers – is to pass major tax reform that lowers the burden on business and makes the U.S. more competitive with other nations. He asserted that corporate inversions – U.S. firms relocating headquarters to other countries with lower taxes – would dry up quickly if companies believed the U.S. was ready to revamp its tax code.

“These inversions do reflect people’s expectations on what taxes will look like, not just today but in the future. They are a symptom of a bigger problem,” he said. “Companies are doing what you expect them to do as rational actors. I am personally convinced you would see fewer inversions with tax reform.”